This invention relates to the manufacture of bags for containing liquids, and to the bags themselves.
Bags such as urostomy bags, urine bags, colostomy bags, etc. are commonly made from two superposed sheets of plastic material welded around their periphery. The weld may be radio-frequency welding or heat welding. It is often desired to have an outlet tube from a lower region of the bag. Such tubes are often also plastic material. One proposal for heat welding a tube to a bag is shown in U.S. Pat. No. 4,023,607 of O. R. Jensen et al. Problems arise when making weld joints to fix the tube to the two bag walls in a leak-proof manner. In particular, there frequently exist two leak paths LP at the locations indicated in FIG. 2 of the accompanying drawings. This problem is particularly acute with bags for containing urine because urine has a low surface tension and will readily find any leak path. Welding a plastic tube between bag walls is a particularly difficult problem when one is employing multi-film laminate material for each bag wall, some of the layers of the laminate being intended to provide strength and liquid impermeability and one or more layers of the laminate being particularly directed to providing gas impermeability. In the contest of a rate of manufacture of bags of up to 2000 per hour, and using a thin multi-laminate bag wall, joining such a wall to a tube of appreciable wall thickness presents difficulties in delivering a suitable amount of heat both to the thin bag wall film and to the relatively thick tube wall.